The National Weather Service said warming brought by a strong, upper-level high centered over the Great Basin would peak on Tuesday and Wednesday. Excessive heat warnings will be in effect most of Tuesday across the deserts, the NWS said.

The coast remained cool, however, and some points had highs in the 60s or low 70s, which contrasted sharply with temperatures near 100 in communities just a few miles inland.

Forecasters also warned that the heat, combined with low humidity levels, will elevate the fire danger. Firefighters jumped on several small fires Monday in San Bernardino, San Diego and Los Angeles counties.

Dry lightning will add to fire worries as a flow of monsoonal moisture arrives from the southeast later in the week, affecting Southern California and the southern Sierra Nevada, the NWS said.

In the Eastern Sierra, temperatures could top 100 degrees in the next few days, accompanied by strong winds and the chance of rainless thunderstorms as early as Tuesday, said state fire Battalion Chief Julie Hutchinson.

"We don't need lightning in that area," she said. "That could be a very bad thing."

Citing the critical fire weather and the dryness of vegetation, the California Department of Forestry and Fire Protection suspended burning permits and other uses of open fire on state responsibility lands in San Diego and Imperial counties. Use of campfires was restricted to established sites in campgrounds.

The weather also brought air pollution concerns.

Los Angeles County health officials advised that air quality Monday was unhealthy in the Santa Clarita Valley and East San Gabriel Valley for people with sensitivities due to conditions such as heart disease, asthma or other chronic respiratory diseases. They were urged to stay indoors if possible and avoid outdoor physical activity.